TAR TREE, AUSTRALIAN CASHEW NUT TREE, SEMECARPUS AUSTRALIENSISThe Tar Tree or Australian Cashew Nut Tree is so named because of its ‘fruits’ and seeds or nuts. And the fact that the bark when cut exudes a black tar-like substance. Tourists are warned to stay clear of this tree as touching any part of it can cause severe allergic reactions on the skin and if you rub your eyes after handling the fruit, seeds or black sticky sap then you could go blind. The aboriginal people of Australia protect their hands with clay before touching the fruit and nuts.
The Australian Cashew Nut tree is native to Australia, Papua New Guinea and the Torres Strait Islands. It grows in open forest or rainforests and looks rather like a mango tree. In this it is very different from Semecarpus anarcadium a close relative which grows in India, Pakistan and Nepal mainly in the Himalayan regions of those countries. It is also different in that the Indian subcontinent’s tree has been the subject of many medical tests, whereas few have been done of the Australian cashew nut tree. However the enterprising Australians have been looking at ways to remove the toxins in the nuts so that they can be sold commercially.
The nuts if eaten can prove fatal although the fleshy orange stem which is the “fruit” to which the nuts are attached may be eaten by some individuals it seems, without any ill effects. However, the aboriginal peoples of Australia bake the bright orange fruits before eating them, and it is reported that they are sweet. The nuts can be eaten if they are leached of their toxins, so these are traditionally soaked in several changes of water for between 2 and 7 days before being heated in bark and eaten like a cashew nut, which they allegedly taste like. If you eat the nut raw then be prepared to have mouth ulcers.
The toxins are believed to be urushiols which are similar components to those found in poison ivy (Toxiodendron radicana), which is why the tree is best avoided.
I have nibbled on extremely ripe fruit which were larger and fuller than those in your photos. The fruit is very aromatic, somewhat like a good persimon. I am extremely wary of the sap and only nibbled enough for a taste. about 15 minutes later, there was a slight burning sensation, no worse than I get from common mangos. I do however fear development of a permanent allergy, something that suddenly happened to a mango eating family member after eating a wild mango. The semecarpus australiensis tree was in a gallery rainforest near Cairns. In summary, if the fruit was not questionable, it would be the king of native fruits in my opinion.
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